1. Technical Field
The present invention relates to a liquid storage tank and, in particular, to a liquid storage tank equipped with a circuit chip positioned at a predetermined position of a tank main body that stores a liquid. The liquid storage tank is also equipped with a connection terminal plate having a chip contact piece for pressing and making contact with a chip contact point on the circuit chip and for conductively connecting the chip contact point to a contact point of another circuit.
2. Related Art
The description below is given in the context of liquid consumption devices that employ liquid in, e.g., a recording operation. A common example of such a liquid consumption recording device is an ink jet printer, where the recording operation is usually a printing operation, the liquid used is ink, and the liquid storage tank is an easily changeable ink cartridge.
An ink supply opening is provided to a cartridge case (tank main body) storing a predetermined amount of the ink liquid in the ink cartridge for the ink jet type recording device. When the ink cartridge is attached to a cartridge attached portion of the printer, an ink supply needle equipped in the cartridge attached portion is inserted into and connected with the ink supply opening. This enables to supply the stored ink liquid to the printer.
The ink jet recording device performs recording of images and characters by sending the ink supplied from the ink cartridge to a recording head and by ejecting and applying an ink drop to a recording medium such as a paper by the recording head.
In the recording head of such an ink jet type recording device, the ejection of the ink drop is controlled by using heat or vibration. If an ink ejection operation is attempted, however, when the ink cartridge is empty and unable to supply ink (also referred to as an empty ejection), there is a possibility of failure.
Consequently, in the ink jet type recording device, it is necessary to watch the remaining amount of the ink liquid in the ink cartridge to prevent the empty ejection by the recording head.
Further, for example, when the recording device is to be used for different purposes like printing full color photographs in addition to monochrome text printing, the consumption rates and amounts of the different colors vary. Accordingly, in some of the recent ink jet type recording devices, there are a plurality of ink cartridges which can be individually exchanged so as to put into the recording device the kinds of ink cartridges suited for the use to which the recording device is to be put. In the case of such an ink jet type recording device, where cartridges can be used, removed, and used again, multiple times, it is necessary also to manage whether cartridges are new or used, and to manage how much ink has been used from cartridges. This kind of information may be thought of as a “used record”.
Due to such a background, in the recent ink cartridge, various types of ink cartridges have been proposed. For example, an ink cartridge equipped with remaining amount detecting means for outputting a predetermined electric signal when the remaining amount of the ink liquid stored in the tank main body is consumed to a preliminary set threshold value or information recording means (memory) by which a control unit of the printer can write and read the information such as a type of the ink and the using record.
The ink remaining amount detecting means and the information storing means mounted in the ink cartridge are respectively prepared as a circuit chip made into one chip in consideration of assembling property of various ink cartridges to the tank main body, standardization of parts, and the like.
Then when the ink cartridge is designed, a device for saving the troubles of wiring and the like when assembling is required by, for example, conductively connecting a chip contact point equipped on the circuit chip as the remaining amount detecting means to a chip contact point of another circuit (for example, a circuit chip as information storing means) by using a connection terminal plate made of a metal plate.
FIG. 13 is an example of a conductive structure of a pair of chip contact points 2a, 2b on a sensor chip (circuit chip) 1 assembled to the tank main body as the remaining amount detecting means and a pair of chip contact pieces 5a, 5b of a connection terminal plate conductively connecting these chip contact points 2a, 2b to another circuit in the conventional ink cartridge.
The conductive structure shown here is same as the conductive structure shown in JP-A-2001-146030. A chip main body 1a in a flat rectangular solid state is a vibration plate and the upper surface of the chip main body 1a is a flat connection outer surface 1b on which the pair of chip contact points 2a, 2b are disposed in the sensor chip 1. A piezo element 6 as a piezoelectric element is disposed at the center of the chip main body 1a and an upper electrode 3a and a lower electrode 3b disposed at upper and lower sides of the piezo element 6 are respectively connected to the chip contact points 2a, 2b. 
The pair of chip contact points 2a, 2b are equipped near a pair of opposite sides of the connection outer surface 1b as shown in FIG. 13. Each chip contact 2a, 2b is provided so as to be apart from the adjacent edges of the connection outer surface 1b by proper distances L1, L2.
The pair of chip contact pieces 5a, 5b are a part of the connection terminal plate respectively formed by press formation of a metal plate. A tongue portion 5c extending on the connection outer surface 1b from one side of the connection outer surface 1b is formed to the distal end of each chip contact piece 5a, 5b. As shown in FIG. 14A, conductive connection with the chip contact point 2a, 2b is accomplished by making contact the tongue portion 5c of the distal end to each chip contact point 2a, 2b in the state where the proximal side is elastically deformed.
However, in the ink cartridge having the conductive structure shown in FIG. 13, the position of the chip contact piece 5 may be misaligned in the direction in which the length of the tongue-shaped portion 5 of the chip contact piece 5 extending on the connection outer surface 1b is reduced as shown by the arrow X in FIG. 14B due to the assembling error of mutual parts, size tolerance of each part, and the like when assembled to the tank main body. In this case, the contact of the tongue portion 5c to an edge 1c of the connection outer surface 1b prevents the tongue portion 5c from making contact with the chip contact point 2b or reduces the contact pressure, even when the contact is made, resulting in electric connection problems. Accordingly, the design of sensor chip 1 leaves room for the possibility of operational faults.
Two ways described below are considered as methods for preventing the occurrence of such a disadvantage.
One approach is to regulate the positioning and setting of the tolerance of each part. The goal of such an approach is to minimize the positional misalignment of the chip contact pieces 5a, 5b generated by assembling error, size tolerance, and the like of each part is generated in the direction in which the length of the tongue portion 5c of the chip contact piece 5a, 5b extending on the connection outer surface 1b is increased (opposite direction to the arrow X in FIG. 14B).
Another way is to prevent the occurrence of the positional misalignment itself by improving the assembling accuracy by reducing the tolerance of each part or by finely adjusting assembling after each part is attached.
However, the former approach makes it impossible to keep a sufficient gap distance between the tongue portion 5c of the chip contact piece 5a, 5b and the piezo element 6 and the like. That is to say, the former approach introduced a new risk that the upper electrode 3a would make contact with the chip contact piece 5.
On the other hand, in the latter approach, the manufacturing cost of the ink cartridge might be considerably increased due to the increase of the manufacturing cost of each part, and the impact on productivity caused by having to devote more labor to the fine adjustment operation of the assembling position.
Further, in spite of applying such responses, for example, when the length of the chip contact point 2b along the positional misalignment direction and the edge of the connection outer surface 1b is elongated by an anticipated amount in anticipation of the positional misalignment in the direction shown by the arrow X in FIG. 14B, there exists a problem in that the size of the sensor chip 1 is enlarged, possibly resulting in the upsizing of the ink cartridge to which the sensor chip 1 is assembled.